Terfenadine is a pharmaceutical product with an antihistaminic activity.
Processes for preparing terfenadine are known and are described, for example, in Italian patent application 21674 A/87 filed on May 25, 1987 by the present applicant.
It is also known, as described in U.S. Pat. No. 4,742,175, that terfenadine crystallizes in two different polymorphic forms, and can be prepared in the form of the high-melting and the low-melting polymorphic product. The low-melting polymorph has a melting point of 146.degree. C. The high-melting polymorph, which is also the product mostly requested by the pharmaceutical industry, has a melting point range of 149.degree.-151.degree. C.